Russia's Prosecutor-General's Office has asked the U.S. Justice Department for regular updates about the circumstances surrounding the death of a Russian boy adopted by an American family.

A spokeswoman said on February 21 the office was awaiting the autopsy results from Ector County, Texas, where 3-year-old Max Shatto -- known in Russia as Maksim Kuzmin -- died last month.

However, Ector County Sheriff Mark Donaldson told RFE/RL that Russian officials wouldn't be allowed to participate in his investigation.

Shirley Standefer, Ector County's chief medical examiner, told RFE/RL there were bruises on the boy's body, but she could not yet say if they were caused by abuse.

Russian Foreign Ministry official Konstantin Dolgov said on February 21 there were reasons to believe the boy died of "cruel and inhuman treatment."

According to Dolgov, the boy's case will be on the agenda of a meeting between Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry next week.

The boy and his 2-year-old biological brother, Kirill, were adopted by Laura and Alan Shatto late last year.

Concern For Younger Brother

Sheriff Donaldson said Laura Shatto told investigators she had left her two sons unattended only for a few moments as they played together in the family backyard.

She reportedly said that when she returned, the older boy was on the ground and unresponsive. He later died in the hospital.

Child-welfare authorities in Texas say they have opened their own inquiry into child-abuse and neglect allegations. The officials say their priority is to ensure the safety of the second child, who remains with his adoptive parents.

The children's biological mother, Yulia Kuzmina, told Russian television on February 20 that she had appealed to Russia's children's rights ombudsman, Pavel Astakhov, for her parental rights for Kirill to be restored.

"I want my second son to be taken away from those adoptive parents so he escapes the fate of my first son. I am conscious of my guilt now, I know that I'm guilty toward my children, and I will do all I can to fix that, at least with Kirill," Kuzmina said.

Bill Bistransky, acting general consul at the U.S. Embassy in Moscow, said in an interview the boy’s adoptive mother has access to Kirill “under the supervision of local child services.”

The U.S. diplomat in Moscow said Kirill was “safe” with his adoptive family in the U.S.

"[The authorities] have made a preliminary decision that [younger brother] Kirill is safe with his father, so why should he be sent back [to Russia] when he has a father and a family there [in the United States]?" Bistransky said.

The case has provoked strong reactions and extensive media coverage in Russia.

Astakhov wrote on Twitter on February 18 that the boy had been "murdered" by his adoptive mother. However, Astakhov later acknowledged that the investigation into the boy's death had not yet been completed.

Russian lawmakers in the State Duma observed a minute of silence in the child's honor on February 19.

In December, Russia passed a law banning adoptions of Russian children by U.S. citizens.

The head of the Duma's Foreign Affairs Committee, Aleksei Pushkov, said this week that the boy's death meant the issue of the adoption ban was "closed."